A conventional system for this type of electromagnetic solenoid valve device is shown and described in Japanese Patent No. 63-3583. This electromagnetic solenoid valve device will now be explained by reference to FIGS. 3 and 4 of the subject application.
As shown in FIG. 3, the electromagnetic valve includes a pneumatic body member 1 having an internal hole 1a which includes a central opening pointing upward. A pair of components consisting of a first intermediate body 2 and a second intermediate body 3 are inserted into the inner hole 1a. The second intermediate body 3 is inserted into the inner opening formed in the first intermediate body 2 and is fixedly held in place by a retaining ring 4. Thus, the intermediate bodies 2 and 3 are disposed with the inner portion of the body 1. The numeral 11 designates a first exhaust port, the numeral 12 is a second supply port, and the numeral 13 is a third delivery port.
The central opening of the second intermediate body portion 3 which has a plurality of steps and includes balancing chamber 20 having a relatively large diameter and includes a first chamber 21 having a relatively small diameter. The first chamber 21 is directly connected to the first exhaust port 11. The upper portion of the first intermediate body 2 includes a third chamber 23, while the lower portion includes a second chamber 22. As shown, the second chamber 22 is directly connected to the second port 12, while the third chamber 23 is directly connected to the third port 13 as well as the balancing chamber 20 via feedback passageway 14.
The central opening in the second intermediate body portion 3, i.e., balancing chamber 20 and the first compartment 21, accommodates a lower portion of a movable valve 25 which is adapted to slide freely and is designed to maintain an air-tight seal. The movable valve 25 is provided with a central passageway or connecting path 25a along longitudinal axis. The connecting path 25a has a top opening facing toward the front end of the second chamber 22 and a lower opening facing toward the rear end of the first chamber 21.
A second biasing spring 26 pushes or urges the movable valve 25 upwardly as viewed in FIG. 3. That is, the front surface of movable valve 25 is pushed upwardly in such a way that the movable valve will become seated on a stationary valve seat 24. The second biasing spring 26 is located between the second intermediate body portion 3 and the movable valve 25. The force of the spring is designed to provide a predetermined load.
The upper end of the intermediate body 2 rests against the lower end of a stationary iron core 30 which has an inner longitudinal hole in which the movable valve seat 31 is inserted and is slidable therein while maintaining air-tight seal. The top end of the movable valve moves relative to the stationary valve seat 24 and is adapted to engage and seat against the top surface of the movable valve 25.
The upper end of the movable valve 31 is disposed within or is inserted into the lower end of the movable iron core 32 and is fixed thereto in a suitable manner. A first biasing spring 33 is caged between the underside of the enlarged end of the movable valve seat 31 and upper end of the stationary iron core 30. The biasing spring 33 applies an upward force to the movable valve seat 31 which is in direction opposite to the magnetic attractive force emanating from the movable iron core 32.
The center passage portion formed along the longitudinal axial of the movable valve seat 31 and movable iron core 32 make up a breathing or aspirating passage which has one end at the top end of the movable valve seat 31 and has the other end opened at the bottom end of the movable iron core 32 to interconnect the upper and lower surrounding chambers 35 and 36.
As shown in FIG. 3, numeral 40 is a holding plate, numeral 41 is a guiding body, numeral 42 is an insulative bobbin, numeral 43 designates an electrical solenoid, numeral 44 designates a protective cover, numeral 45 is a stopper member, and numeral 46 is a retaining or stopper ring.
The operation of the electromagnetic valve device of FIG. 3 will be explained with reference to the curves of FIG. 4. As shown, FIG. 4 depicts the relationship between the stroke of the movable valve seat 31 and the biasing forces of the first and second springs 33 and 26, respectively, which is illustrated on the right-hand side of FIG. 4, and the relationship between the magnetizing current and magnetic force of electrical solenoid 43 which is illustrated on the left-hand side of FIG. 4. Initially, when the solenoid 43 in FIG. 3 is demagnetized, the movable valve seat 31 is unseated from movable valve 25 by the force exerted by the first biasing spring 33, and the movable valve 25 is seated against the stationary valve seat 24 by the force exerted by the second spring 26. Therefore, the first port 11 and the first chamber 21 along with the third port 13 and the third chamber 23 are connected while the second port 12, and the second chamber 22 will be closed. We will refer to this condition as a first position or position A.
As the magnetizing current supplied to the electrical solenoid 43 is increased, a magnetic force or field strength conveyed to the movable iron core 32 will proportionally increase. However, as shown in FIG. 4, when the magnetizing current is within range X, the magnetic force which is represented by curve F32 does not exceed the spring force as represented by curve F33 which is exerted by the first spring 33. Thus, the bottom end of movable valve seat 31 cannot become seated on the movable valve 25 and therefore the valve remains in position A.
When the magnetizing current continues to increase, the magnetic force F32 will eventually reach the level of the spring force F33 so that the bottom end of the movable valve seat 31 is moved onto the top end of the movable valve 25 so that the first port 11 and the first chamber 21 as well as the third port 13 and the third chamber 23 are shut off. Thus, all three ports 11, 12, and 13 are isolated or shut off since the valve is in lap position. At this time, the force shown by curve F26 which is exerted by the second spring 26 is working against the magnetic force F32. Therefore, the total exerting force shown by curve F50 which is a combination of both springs 33 and 26 maintains the valve in the lap position even though the magnetizing current continues to increase. This is illustrated by the range Y in FIG. 4.
Now, as the magnetizing current continues to increase the magnetic force F32 will eventually overcome the total spring force F50 and will enter the range Z. Thus, the movable valve 25 will remain seated on the movable valve seat 31 but will unseat the movable valve 25 from stationary valve seat 24, so that the first port 11 and the first chamber 21 will remain shut off. However, the second port 12, the second chamber 22, and the third port 13 and the third chamber 23 will become connected. We will refer to this condition as the second position or position B.
Therefore, one can switch to any one of 3 positions, namely, position A,LAP position, or position B, by controlling the magnetizing current which is selected and outputted by a drive controller as will be described hereinafter. In operation, the positions have been arbitrarily preset in X, Y, and Z magnetizing current ranges as either position A setting value, LAP position setting value, or position B setting value.
In at least one conventional system, however, there has been a problem when one tries to output the actual magnetizing current by the drive controller of the electromagnetic valve device in which stable control can be obtained only when one selects a narrow current range for the LAP position setting value. That is, in viewing FIG. 4, it will be seen that the area Y that is formed when the magnetizing current increases from position A, and when the magnetizing current decreases from position B. This difference causes a phenomenon in which the common range Y becomes smaller than that shown in FIG. 4.
The present invention was made to solve such a problem, and attempts to provide an electromagnetic valve device with a drive controller which is capable of outputting magnetizing currents with precision and stability in controlling the LAP position.